The invention relates to methods and apparatus for communications in a wellbore.
To produce hydrocarbons from a subterranean formation, a wellbore is drilled into the earth. Following drilling, the wellbore is completed by installing completion equipment, including casing, liner, production tubing, packers, valves, and so forth. One or more zones in the well are perforated to enable communication between a target formation and the wellbore. Once perforated, wellbore fluids are allowed to enter the wellbore and flow up the production tubing to the well surface.
In many wells, multiple zones are operated for production of well fluids. To ensure a proper flow profile, valves that can be set at various choke positions are installed in the wellbore to control the fluid flow rate from each zone. For example, differences in pressures of the different zones may cause flow from the higher pressure zone to the lower pressure zone, which reduces fluid flow to the well surface. Valves may be set to control flow rates so that proper fluid flow can occur to the well surface. Also, if production of water or other undesirable fluids occur, some of the valves may be shut off completely to prevent flow from the one or more water-producing zones into the wellbore.
With improvements in technology, wellbores can now be equipped with so called smart or intelligent completion systems, which typically have sensors, gauges, and other electronic devices in the wellbore. The sensors and gauges are used to monitor various well characteristics, including temperature, pressure, flow rate, and formation characteristics. Additionally, downhole components such as valves may be controlled remotely from the well surface or at another remote location. Thus, if any problems occur during production of the well, valves and/or other downhole components may be adjusted to remedy the problem.
To communicate with such downhole devices, a typical arrangement uses a permanent downhole cable (PDC) that is run from the well surface to one or more downhole components. The PDC is used to deliver power to the downhole components as well as to deliver control signals to such components. Additionally, sensors and gauges are able to communicate measurements up the PDC to a surface controller.
Due to the relatively harsh conditions in the wellbore as well as various intervention operations that are performed in the wellbore, there is some likelihood that a PDC can be damaged during its many months or years of operation so that communication of power and signals to downhole components is no longer possible. When that occurs, the downhole components are rendered inoperable.
A need thus exists for a method and apparatus to ensure or increase the likelihood of continued operation of well components even if a communication mechanism such as a downhole cable is damaged.
In general, in accordance with one embodiment, a method of communications in a wellbore comprises determining if a first communications mechanism for communicating with a downhole device is operational, and running a backup communications mechanism into the wellbore if the first communications mechanism is not operational. The method further comprises communicating with the downhole device using the backup communications mechanism.
Other features and embodiments will become apparent from the following description, from the drawings, and from the claims.